Reflector antenna with focusing spherical lens

ABSTRACT

A reflector antenna providing an asymmetrical beam focusing for shortwave radar transmitting and receiving operation, which essentially consists of a multiple curved reflector which rotates at a constant angular velocity, as well as a primary radiation or beam source. Between the reflector and the stationarily constructed primary radiation or beam source, a spherical lens having a relatively large frequency band width which rotates with the reflector, and wherein the beam extends in circularly edged transverse planes intersecting the rotational axis. The spherical lens may be constructed to serve as a rotary coupling for the transfer of the beam power, and to concurrently serve as a condenser for illumination of the elliptical reflector aperture.

127mm OR 349275407 ilmlie States atent 119] 1111 3,927,407

Beck et al. Dec. 16, 1975 [5 REFLECTOR ANTENNA WITH FOCUS-ING 3,845,483 10/1974 Soma ct al. 343/761 SPHERICAL LENS 3,848,255 11/1974 Migdal 343/911 L [75] Inventors: Gerhard Beck; Siegfried Zeininger,

both of Flensburg, Germany [73] Assignee: Eltro GmbH Gesellschaft fur Strahlungstechnik, Heidelberg, 57] ABSTRACT Germany Primary ExaminerEli Lieberman Attorney, Agent, or Firm-l-laseltine, Lake & Waters A reflector antenna providing an asymmetrical beam [22] Filed: Sept. 6, 1974 focusing for shortwave radar transmitting and receiving operation, which essentially consists of a multiple [21] Appl' 503912 curved reflector which rotates at a constant angular velocity, as' well as a primary radiation or beam [30] Foreign Application Priority Data source. Between the reflector and the stationarily con- Sept. 7, 1973 Germany 2345222 Structed Primary radiation or beam Source, a Spherical lens having a relatively large frequency band width 52 us. c1. 343/754; 343/761; 343/781 which rotates with the reflector, and wherein the [51] Int. Cl. HOlQ 19/06 beam extends in circularly edged transverse Planes [53] Fi l f Search 343/755 7 1 39 911 L, tersecting the rotational axis. The spherical lens may 343/754 781 be constructed to serve as a rotary coupling for the transfer of the beam power, and to concurrently serve [56] References Ci d as a condenser for illumination of the elliptical reflec- UNITED STATES PATENTS apemlre- 3,518,686 6/1970 Siebecker 343/755 4 laim 4 Drawing Figures US. Patent Dec. 16,1975 Sheet 1 of3 3,927,407

US. Patent Dec. 16, 1975 Sheet 2 of3 3,927,407

F/QZ

US. Patent Dec 16, 1975 Sheet 3 of3 3,927,407

FIG. 3b

REFLECTOR ANTENNA WITH FOCUSING SPHERICAL LENS FIELD OF THE INVENTION The present invention relates to a reflector antenna providing asymmetrical beam focusing or collimating for shortwave radar transmitting'and receiving operation, which essentially consists of a multiply curved reflector which rotates at a constant angular velocity, as well as a primary radiation or energy source.

DISCUSSION OF THE PRIOR ART Antennas of the above-described type are known, which incorporate a rotating reflector for the generation of asymmetrical directive or tracking patterns, which is differently proportioned in accordance with height and width, in conformance with the prescribed tracking pattern cross-section, or which consists of superimposed positioned parabolically-shaped or elliptical strips. Also known are rotating horn parabola radiators or reflector antennas providing a large extent of minor lobe damping, which similarly generates asymmetrical directive patterns. Their infeed is effectuated in a vertical direction on the vertical rotational axis and their reflection from the reflector in a horizontal direction.

In these known antennas, which are constructed for a different focusing in both azimuth and elevation, the energy supplying primary generator takes part in the rotation of the antenna. This has the disadvantage that, for effecting the transfer of the transmitting or receiv ing power from a stationary to the rotating portion of the antenna system, a rotary connector or coupling must be built into the antenna power conduit, which can be designed only for discrete frequencies or only for a narrow frequency band and thereby narrowly limits the frequency band width of this antenna.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention in avoiding the aforementioned disadvantages by providing the capability of increasing the frequency band width of an antenna of the above-mentioned type.

The foregoing object is inventively attained in that there is interposed between the reflector and the stationarily constructed primary radiation or energy source, a spherical lens having a relatively large frequency band width which rotates in conjunction with the reflector, and wherein the beam extends in circularly edged transverse planes intersecting the rotational axis. Through this measure there is, in an advantageous manner, facilitated the utilization of an ordinary narrow band rotary coupling. Concerning the operational properties, these remain same for the transmissive, as well as for receiving operation. Merely the direction of the radiation or energy output which is to be transferred and the series sequence in which the individual antenna components are employed is reversed.

An advantageous further embodiment of the invention contemplates that the spherical lens be constructed so as to serve as a rotary coupling for the transfer of the energy output, and to concurrently serve as a condenser for illumination of the elliptical reflector aperture. The advantage which is hereby obtained is the dual function of the wide band-operating spherical lens which concurrently functions as a condenser and which divides the introduced energy power, in accordance with known measures and therefore not further described covering tracking lines in an optimum manner over the generally elliptical reflector aperture.

Further characteristics of the invention provide for that the transfer of the radiation or energy power from the primary energy source to the spherical lens during transmitting operation, as well as in the reverse direction during receiving operation, is carried out across a free space, wherein we hereby deal with a dielectrically heterogeneous spherical lens. It is further preferable that the reflector be constructed for energy or radiation power supplied from externally of the reflector axis. Thereby, shadowing of the aperture by the power supply system is avoided, and feedback from the reflector to the power supply system is eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS Reference may now be had to the following exemplary embodiment of the invention, taken in conjunction with the accompanying drawings in which the various figures thereof have corresponding elements designated by identical reference numerals; and wherein:

FIG. 1 is a schematic illustration of the spatial arrangement of the inventive object;

FIG. 2 is a representation of the essential components of the inventive object shown in a rectangular coordinate system;

FIG. 3a shows the beam aperture of the reflector illumination, respectively, the main aperture angle 01 corresponding to the height of the reflector (parabola); and

FIG. 3b shows the beam aperture of the reflector illumination, respectively, the main aperture angle a corresponding to the width of the reflector (circular).

DETAILED DESCRIPTION Referring now in detail to the drawings, the pointshaped stationary primary radiation or energy source 1 (FIG. 1) is positioned on the rotational axis 2 of the antenna, which is shown in chain-dotted illustration. The rotationally symmetric beam emitted from the primary energy source 1 traverses the rotating component 3, which is functionally formed as a spherical lens and condenser, and is mirrored at reflector 4, the latter of which rotates in unison with the component 3. Since the rotating component 3 has the same spherically curved surface thereof constantly facing towards the stationary energy source, the radiation geometry is maintained during antenna rotation, and the operating properties of the antenna are thus independent of the antenna rotation. The entire radiation or energy emitted from the primary energy source 1 extends within the element 3 in circularly bound transverse planes which intersect the rotational axis, of which there are shown the two cross-hatched planes 5 and 6 in FIG. 1.

In FIG. 2 the reflector 4 is illustrated together with the spherical lens and, respectively, the condenser 3 in a rectangular coordinate system. The arrows herein symbolize the antenna beam. The zaxis is the rotational axis of the antenna system. while in the coordinate plane perpendicular thereto through the point F there are employed polar coordinates r, d). The surfaces of the reflector are described through the equation NI-FZfV-l-Fsin d (f)=4f(f+rcosd (f)) and are formed together by the M cutting curves 4) constant, wherein d) is considered as parameter. The

curves (1) constants are sections of paraboloids with the particular focal widths f,

The two in FIG. 1 shown transverse planes 5 and 6 of the condenser 3 are located perpendicular to each other, are and so dielectrically coated, whereby the radiation or energy emanating from the radiation or energy source 1 is focused in the two virtual focal points F and F shown in FIG. 3. The remaining transverse planes extending through the condenser correspond to the focal points F,, between F and F All focal points of the dielectric condenser concurrently are the focal points of the paraboloids with the focal widths f.

FIGS. 30 and 3]) illustrate the two main aperture angles a, and 01:, which respectively correspond to the height and width of the reflector, and whose crowns respectively lie in the associated focal point. From the reflector equation there are obtained for the special values (I) 90 and d) 180, respectively, a parabola (FIG. 3a), and a circle (FIG. 3b). The magnitude of angles a and a is directed in accordance with the measure of optimum tracking covering lines for the dielectric condenser and for the reflector. For the covering of the large reflector diameter with a correspondingly large radiation focus it has been ascertained, as is known from the Theory of Reflector Parabolae, that an aperture angle a 45 is suitable when the edge dropoff of the coating consists of approximately 10 dB. Furthermore. for obtaining optimum reflector coverings. the covering of the spherical lens operating as a condenser is determined with respect to the reflector movement.

While there has been shown what is considered to be the preferred embodiment of the invention, it will be obvious that modifications may be made which come within the scope of the disclosure of the specification.

What is claimed is:

1. In a reflector antenna providing for asymmetrical beam focusing or collimating for shortwave radar transmitting and receiving operation, including a multiple curved reflector rotating at a constant velocity; and a stationary primary radiation source, the improvement comprising: said reflector including an elliptical reflector aperture, a spherical lens of relatively wide frequency band width being interposed between said reflector and said primary energy source, said spherical lens constituting a rotary coupling for transfer of radiation from said primary energy source and concurrently forming a condenser for illuminating said elliptical reflector aperture, said spherical lens rotating in unison with said reflector, said beam extending through said spherical lens in circularly bound transverse planes intersecting the rotational axis thereof whereby said reflector antenna is adapted to generate an asymmetrical tracking pattern with elliptical cross-section relative to the reflector axis of said reflector antenna evincing a relatively large focusing in the azimuth plane and a relatively small focusing in the elevational plane predicated on the application of said antenna.

2. Reflector antenna as claimed in claim 1, transfer of radiation power from said primary beam source to said spherical lens during transmitting operation and reversely during sending operation being effected through a free space.

3. Reflector antenna as claimed in claim 1, said re flector being adapted to receive radiation beam power from externally of the reflector axis.

4. Reflector antenna as claimed in claim 1, said spherical lens comprising a dielectrically heteroge- 

1. In a reflector antenna providing for asymmetrical beam focusing or collimating for shortwave radar transmitting and receiving operation, including a multiple curved reflector rotating at a constant velocity; and a stationary primary radiation source, the improvement comprising: said reflector including an elliptical reflector aperture, a spherical lens of relatively wide frequency band width being interposed between said reflector and said primary energy source, said spherical lens constituting a rotary coupling for transfer of radiation from said primary energy source and concurrently forming a condenser for illuminating said elliptical reflector aperture, said spherical lens rotating in unison with said reflector, said beam extending through said spherical lens in circularly bound transverse planes intersecting the rotational axis thereof whereby said reflector antenna is adapted to generate an asymmetrical tracking pattern with elliptical cross-section relative to the reflector axis of said reflector antenna evincing a relatively large focusing in the azimuth plane and a relatively small focusing in the elevational plane predicated on the application of said antenna.
 2. Reflector antenna as claimed in claim 1, transfer of radiation power from said primary beam source to said spherical lens during transmitting operation and reversely during sending operation being effected through a free space.
 3. Reflector antenna as claimed in claim 1, said reflector being adapted to receive radiation beam power from externally of the reflector axis.
 4. Reflector antenna as claimed in claim 1, said spherical lens comprising a dielectrically heterogeneous spherical lens. 